Hydrogenation and Emulsions

Question 1

The ingredients of soft margarine include hydrogenated vegetable oil. Why is hydrogenated vegetable oil used in soft margarine? (1 mark)

Answer 1

any one from:
• have a higher melting point than (vegetable) oil
• are solid at (room temperature) /hardened / harder

Question 2

Describe how vegetable oils are hydrogenated. (2 marks)

Answer 2

any two from:
• hydrogen added
• to carbon carbon double bond / to saturate
• (nickel) catalyst / temperature 60 - 150°C

Question 3

What type of fat contains double carbon carbon bonds? (1 mark)

Answer 3

(poly)unsaturated

Question 4

Unsaturated vegetable oils can be hardened to make them useful as spreads. Describe how unsaturated vegetable oils are hardened. (2 marks)

Answer 4

(react) with hydrogen / H2 /hydrogenation
any one from:
- heated / 60°C
- catalyst / nickel

Question 5

What do the E-numbers indicate? (1 mark)

Answer 5

permitted additive / (added) chemicals
or
names / types of additives

Question 6

To detect unsaturated fats, a small amount of bromine or iodine solution can be added. What happens to show that an unsaturated fat is present? (1 mark)

Answer 6

turns colourless / decolourises

Question 7

Sunflower oil can be hardened so that it can be used to make margarine. Explain how sunflower oil can be hardened. (3 marks)

Answer 7

any three from:

• (react with) hydrogen
• with a (nickel) catalyst
• at about 60°C
• increase the melting point

Question 8

Oils can be hardened by reacting them with hydrogen. A student said that hardening would make sunflower oil healthier. Is this student’s hypothesis correct? Explain your answer. (2 marks)

Answer 8

no, because hydrogen adds to the unsaturated fat or no, because hydrogen reduces the number of carbon.carbon double bonds
therefore there will be less polyunsaturated fat

Question 9

Explain how the molecules in the egg yolk are able to produce a stable mixture of olive oil and water. (3 marks)

Answer 9

molecules in egg yolk act as emulsifiers
because molecules in egg yolk have a head which dissolves in / attracted to water
because molecules in egg yolk have a tail which dissolves in / attracted to oil

Question 10

Describe the property of emulsions that makes them suitable for salad dressings. (1 mark)

Answer 10

They have good coating ability and a thick texture.

Question 11

Explain why plants make and store oils. (2 marks)

Answer 11

Oil and water do not mix well because the long hydrocarbon chains in the oils cannot interact with water molecules, which do not have long hydrocarbon chains.

Question 12

Explain how emulsifiers stop oil and water separating out in emulsions. (4 marks)

Answer 12

Emulsifier molecules have two different ends. One end interacts well with water molecules. This is the hydrophilic end. One end interacts well with oil molecules, and badly with water molecules. This is the hydrophobic end. In an oil-in-water emulsion, emulsifier molecules coat the surface of oil droplets. The hydrophobic ends of the emulsifier molecules interact with the oil droplets. The hydrophilic ends interact with the water. These coatings keep the oil droplets evenly dispersed throughout the emulsion and stop them clumping together to form their own separate layer.